Anesthetic administering apparatus



July 1; 1958 w. w. HAY

ANESTHETIC ADMINISTERING APPARATUS 2 Sheets-Sheet 1 FIG.

Filed March 25, 1955 GAS MACHINE NVENTQR WAYNE W. HAY A ATTORNEY y 1, 1958 w. w. HAY 2,841,142

ANESTHETIC ADMINISTERING APPARATUS Filed March 25, 1955 W FIG. -3

2 Sheets-Sheet 2 FIG. 4

INVENTOR WAY NE W. HAY

. ATTORNEY United States Patent ANESTHETIC ADMINISTERING APPARATUS Wayne W. Hay, Madison, Wis., assignor to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application March 25, 1955, Serial No. 496,782

8 Claims. (Cl. 128-188) This invention relates to apparatus for administering inhalant anesthetics, and more particularly to semi-open circuit, or non-rebreathing type, anesthetic administering apparatus.

The so-called non-rebreathing" anesthetic administering apparatus is characterized in that the delivery side of the circuit through which the patient inhales, during administration of the anesthetic, is confined from the ambient atmosphere and includes a reservoir bag which is subjected normally to the ambient atmospheric pressure. The exhalation gases are discharged to the atmosphere and are not recycled within the breathing circuit as in certain other types of anesthetic breathing circuits. Administration in this type of circuit differs from the opendrop method wherein the inhalation gases are not confined or isolated from the ambient atmosphere.

As a result of the operation inherent in such an anesthetic administration circuit, a problem arises when it becomes necessary or desirable to assist the patients respiration. In closed anesthetic administering circuits, for example, the anesthetist may assist respiration by compressing the reservoir, or breathing bag, thereby creating positive pressure in the circuit and allowing the gases to be forced into the patients lungs during each inhalation. However, it is not possible in the usual type of non-rebreathing apparatus to do this because in its normal operation the exhalation outlet of the circuit is vented to the atmosphere when positive pressure is applied thereto, thus preventing positive inflation of the patients lungs.

It has been the practice in some cases, wherein it has been desired to assist the patients respiration while using a non-rebreathing circuit, for the anesthetist to manually occlude the discharge opening while simultaneously applying pressure to the breathing bag. Thus by proper manipulation such positive pressure could be applied by the anesthetist at intervals coordinated with the inhalations of the patient. However, this procedure is somewhat tedious and is not completely satisfactory inasmuch as it requires considerable attention on the part of the anesthetist and necessitates the use of both of his hands.

Consequently, not only is the anesthetists ability to recognize and meet other emergencies hindered, but he is placed under a severe strain to perform his usual duties.

An object of the present invention is to provide an improved anesthetic administering apparatus of the nonrebreathing type which is capable of affording assisted respiration during anesthesia with a minimum of effort on the part of the anesthetist.

A further object'of the invention isto provide an improved anesthetic administering apparatus of the nonrebreathing type having means for controllably producing positive pressure within the administering circuit, and for sustaining such pressure without requiring further manual adjustments by the anesthetist.

A further object of the invention is to provide in an anesthetic administering apparatus having an exhalation discharge outlet to the atmosphere, means functioning 2,841,142 Patented July 1, 1958 automatically in response to positive pressure to prevent the dissipation thereof by discharge through the exhalation outlet.

A further object of the invention is to provide such an anesthetic administering apparatus wherein the means controlling the direction of flow of the patients respira tion, and the means for automatically functioning to permit the delivery of inhalation gases under positive pressure to the patients lungs are embodied in a compact structure of simple manufacture and which is readily interchangeable with the elements of standard anesthetic breathing equipment.

A still further object of the invention is to afford a high degree of safety in apparatus of this type, such that inadvertent over-inflation of the patients lungs will be substantially impossible.

In accordance with the present invention there is pro vided in an anesthetic administering circuit of the nonrebreathing type, means for controllably delivering gas to the patient under positive pressure and means responsive thereto, effective to occlude the expiratory discharge opening whereby inhalation gas may be forced into the patients lungs. .In a preferred embodiment, exhalation and inhalation valve means, for controlling the exhalation and inhalation gas flows, respectively, in the breathing circuit, and pressure responsive means for occluding the exhalation discharge opening are incorporated in a compact unitary valve housing adapted to be connected with a face mask or other inhaler device and with a source of anesthetic gas. The valve housing preferably includes a pressure actuated diaphragm having means for rendering such diaphragm responsive to the delivery of gas pressure upstream of the inhalation control valve whereby positive delivery pressure actuates such diaphragm to effect the closing of the exhalation valve control means. The preferredrconstruction also includes a pressure relief device associated with the pressure responsive diaphragm for limiting the delivery gas pressure to a predetermined maximum positive pressure, and a selector adapted to be selectively positioned, either to inactivate said diaphragm or to render the diaphragm operative in response to said positive delivery pressure.

The invention and other of its advantages will be more readily understood by reference to the following description of a preferred embodiment thereof and the accompanying drawings in which:

Fig. 1 illustrates an anesthetic administering apparatus, of the non-rebreathing type, including a preferred arrangement for facilitating assisted respiration of the patient;

Fig. 2 is a cross-section view, in elevation, of a simplified valve housing showing inhalation and exhalation control check valves for controlling the direction of gas flow during respiration, and the pressure responsive closing means associated with the exhalation valve;

Fig. 3 is a sectional view of the valve housing, taken along the line 33 in Fig. 2, looking in the direction of the arrows, illustrating some details of the exhalation check valve construction and of the exhalation discharge outlet;

Fig. 4 is a sectional view taken along the line 4-4 in Fig. 2, looking in the direction of the arrows, illustrating a portion of the selector'device for inactivating and venting the pressure responsive means associated with the exhalation check valve;

Fig. 5 is a partial section of the valve housing taken along line 5-5 in Fig. 3, illustrating the location of the exhalation discharge openings therein;

Fig. 6 is a partial sectional view illustrating an alternative construction of a portion of the valve housing and of the venting means associated with the pressure responsive diaphragm; and,

Fig. 7 is a partial sectional view illustrating an alternative embodiment of the pressure responsive means.

Referring now to the drawings, apparatus of the nonrebreathing type suitable for the administration of anesthetic gases, in accordance with a preferred form of the present invention, is illustrated in Fig. 1. The apparatus includes a gas machine, indicated schematically at M, which is of well-known construction, whereina suitable anesthetic gas mixture is formed for delivery to the patient. The machine M includes supplies of the necessary gases and/or volatile anesthetic agents, and suitable valve means which permit the anesthetic gas mixture to be delivered only in the direction shown, to the patient. Typical anesthetic mixtures which are used, during anesthesia, are mixtures of oxygen and gaseous anesthetics such as cyclopropane, nitrous oxide, etc., or mixtures of oxygen and/or air with the vapors of volatile anesthetic agents such as diethyl ether, trichloroethylene, etc.

The outlet of the gas machine leads to a T-fitting 10 having a reservoir bag 12 attached to one of its legs and a conduit 14 connected to its other leg. The conduit 14 is in turn connected to the inlet of a non-rebreathing valve 16 which is seated on a funnel-shaped face mask 18 whereby the anesthetic mixture may be delivered to the patient P. The face mask has a hook ring 20 to which the ends of a strap 22, which passes behind the patients head, are attached so as to secure the mask in its operative position, as shown. Discharge openings 24 are provided in the housing of valve 16 through which the patients exhalation gases are passed to the atmosphere.

Although the face mask has been shown in the present embodiment as the inhalor for confining the 'patients gases of respiration and for connecting the external portions of the non-rebreathing circuit to the patients respiratory tract, it will be understood that other well-known types of inhalors may be used in its place. For example, the mask 18 may be replaced by an endo-tracheal tube, to which the outlet of the valve 16 would then be directly attached. Such type inhalors are frequently preferred because they reduce the dead-space in the breathing circuit and help to minimize rebreathing of the exhalation gases.

As will be more fully understood hereinafter, the valve 16 includes valve elements which function in response to the patients own breathing efforts to regulate the direction of gas flow within the circuit. Thus, during the inhalation phases the anesthetic gas mixture is drawn inwardly by the patient through conduit 14, valve 16 and thence mask 18. The valve means controlling the direction of gas flow prevents the entrance of atmospheric air through the openings 24 during inhalation. Upon subsequent exhalation the patients exhalatory eifort closes off the delivery conduit 14 and effects the opening of the outlet 24 to the atmosphere.

The reservoir bag 12 forms an expansible chamber in the delivery system of the anesthetic administering circuit, in which gases delivered thereto may be accumulated, causing the bag to expand as indicated at 12', while maintaining substantially atmospheric pressure. Normally the gas machine M is adjusted to deliver an anesthetic gas mixture at the desired rate and the bag 12 is thus expanded during each exhalation of the patient when such mixture is being supplied to the delivery conduit and is not being withdrawn therefrom by the patient. During inhalation the bag is deflated as the gas volume therein is supplied to the patient. The reservoir, or breathing, bag provides a ready means for the anesthetist to produce a positive pressure in the delivery passages, which is accomplished simply by squeezing the bag. The extent of the delivery pressure created is a function of the degree to which the bag is compressed and is readily ascertainable by the anesthetist through the feel of the pressure exerted on the bag. The reservoir bag need not be connected as a branch of the delivery conduit as shown but may be connected, alternatively, in series therewith,

whichever is more convenient. Such expedients are well known.

The valve 16 is shown in greater detail in Figs. 2, 3, 4 and 5. This valve comprises a tubular inlet 26, on which the delivery conduit 14 is received, which intersects a tubular housing 28, substantially at right angles, and opens into a breathing chamber 29 formed therein. The lower portion of the housing 28 is reduced at 30 forming an outlet adapted to be received in a suitable opening in the face mask 13. A check-valve 31 disposed at the inner end of inlet conduit 26 forms an inhalation valve. This valve may be of any conventional construction, but preferably is a flap-type check valve, as shown, in the form of a preassembled insertaole unit. This structure includes an annular sleeve 32 of rubber or other suitable, resilient material which may be pressed into the end of conduit 26 in a gas-tight manner. Radial spokes 34 projecting inwardly from the annular sleeve form a hub 36 substantially centrally therein, in which a flap-type, check-valve element 38 is supported. The perimeter 40 of the valve element 38 is inclined inwardly and seats normally against the annular end face of the valve sleeve 32, such initial seating stress, however, being substantially negligible. Upon inhalation the edge 40 of the valve element is deflected inwardly as shown in dotted lines. A second valve 44 positioned at the top of valve housing 28 forms an exhalation check-valve and is of the same type as the inhalation valve 30. The exhalation valve is carried in a retainer cup 46 that is mounted on the end of tubular housing 28, such as by soldering. The bottom of the retainer cup is perforated as shown at 47 in Fig. 3, forming a series of radial spokes 48 having a central hub 49 in which a flap-type valve element 50 is supported. The peripheral edge of the valve element 50 seats against an annular seating surface of the retainer cup 46, in the same manner as the inhalation check valve. Upon exhalation, the valve element is deflected upwardly to allow the exhalation gases to pass to the atmosphere through the openings 24. The openings 24, in the retainer cup, it will be seen by referring to Figs. 3 and 5, are four in number and are formed by cutting away, such as by milling, the sidewall of the reduced, cylindrical wall-section 52 of the retainer cup. Four flats designated at 54, 55, 56 and 57 in Fig. 3 are thus formed which define the respective openings 24.

A flexible diaphragm 60 is disposed in confronting relation to the exhalation check valve 46 and is so spaced therefrom that, when actuated by positive pressure at its upper face, it is adapted to transmit a downward force through a disc member 61 to the seating portion of the exhalation valve. A valve bonnet 62, received in the upper side of the retainer cup 46, is secured therein by means of a threaded ring 64 and is pressed, around its annular flange 66, against the peripheral portion of the diaphragm 60 to form a gas-tight seal therewith. The

. diaphragm cooperates with the valve bonnet to form a diaphragm chamber 68 within the bonnet to which gas pressure for actuation of the diaphragm may be delivered. An opening 7 0 in the upper Wall of the valve bonnet provides a passage through which the diaphragm chamber may be placed in communication with the atmosphere. A tube 72 received in the bonnet, also communicating with the diaphragm chamber, extends outwardly therefrom and into the delivery conduit 26. The tube 72 is removably inserted through an opening in the wall of the inlet conduit and is provided with a gas-tight coupling arrangement comprising an elastic band 74 having an opening tightly surrounding the tube 72 which is stretched over the inlet 26. This arrangement for connection of tube 72 with the inlet conduit 26 facilitates dismantling and assembly of the valve bonnet.

The force exerted by the diaphragm 60 is equal substantially to the product of the differential pressure acting thereon and the effective area of the diaphragm. In

the construction shown there is also a small additional force acting downwardly against the exhalation valve as the result of the weight of the disc member 61 and the residual weight of the diaphragm which may exist in the event the diaphragm is sufiiciently slack to normally rest on the top of the disc member. However, the force resulting from the weight of these members is negligible insofar as the operation of the exhalation valve is concerned and produces substantially no restriction to exhalation therethrough. The displacement of the diaphragm to close the exhalation valve is therefore solely a function of the differential pressure acting thereon.

The effective area of the diaphragm 60 is substantially equal to the area of the opening of the diaphragm chamber 68 confronting the diaphragm. In certain types of diaphragms the effective area may also be afiected by the construction of the diaphragm element itself, as is well understood. As will be more fully understood hereinafter, the effective area of the diaphragm 60 is larger than the effective area of the exhalation check valve against which it acts, in opposition to the force produced by the gas pressure within the valve chamber 32 tending to open the exhalation valve. Thus, as a result of such proportioning of the diaphragm 6t) and of exhalation valve 46, the diaphragm is adapted to produce a net downward force tending to close the exhalation check valve even though the pressure differentials acting on the diaphragm and on the exhalation check valve are equal.

Mounted within the valve bonnet 62 is a rotatable valve element 76 which has a rotatable spindle 78 extending outside of the bonnet, and a raised cylindrical boss 80 eccentrically disposed with respect to the spindle 78 and the axis of rotation of the valve element, which bears against the top, inside of the bonnet. The boss 80 is seen by the cylindrical section in Fig. 4, and the axis of rotation of the valve is designated at 82 in the same figure. The valve 76 is retained in the valve bonnet by means of an expanding spring clip 84 which snaps into an annular groove within the bore of the bonnet. An annular washer 86, bears against the inwardly projecting portion of the spring clip and receives against its upper side a screen disk 88. A spring 90, resting at its lower end on the center of the screen, extends into a bore 92 in the spindle and is under a slight compression so that the pressure exerted by the spring against the end of the bore urges the valve element 78 upwardly and thus maintains the upper surface of the raised boss 80 in frictional contact with the inner top face of the valve bonnet.

The raised boss 88 of the valve element is spaced inwardly from the surroundinginner walls of the valve bonnet and defines an upper portion 68a of the diaphragm chamber. This portion of the diaphragm chamber is connected by means of an opening 96 in the valve element with a recess 98 in the bottom face of the valve element which confronts the main section of diaphragm chamber 68 and communicates therewith through the openings of the screen 88. The screen 88 serves the dual purpose of supporting the base of spring 90, and of filtering any gases passing therethreugh to prevent the accession of solid particles to the diaphragm 60.

It will now be seen that the diaphragm chamber 68 may, alternatively, be placed in communication with the atmosphere, or with the delivery inlet at a point upstream of the inhalation check valve. This is accomplished by rotation of the valve spindle 78 so that the raised boss 80 of the valve element is positioned either under the opening 70, as seen in Fig. 2, closing the passage 70 to the atmosphere and connecting the chamber to the delivery inlet through tube 72; or by positioning boss 80 under the inlet end of tube 72, thus sealing the tube 72 and opening the chamber to the atmosphere through passage 70.

As shown in Fig. 4, the selector valve has been rotated to an extreme clockwise position determined by the engagement of the boss 80 with a suitable stop' device such as the pin 100, which may be constructed so as to project inwardly from the top of the valve bonnet. In this position the boss occludes the passage 70 and places tube 72 in communication with the diaphragm chamber. In the opposite extreme position, the boss 80 again comes into contact with the limit stop 100, in which position, as indicated by the outline of the boss 80 in Fig. 4, the opening into the tube 72 is occluded while at the same time, the passage 70 is open. It will be evident, by referring to Fig. 4, that the vaive 76 may be placed intermediate either of the opposite extreme positions in which both the opening 70 and the opening to the tube 72 are communicating with the chamber 68 and in which thesizes of the communicating openings will vary proportionately according to the position of the boss 80.

Having now described a non-rebreathing anesthetic administering apparatus constructed in accordance with a preferred embodiment of the invention, its operation is as follows:

After the customary checking has been done as to the proper functioning of the apparatus, the anesthetist adjusts the selector valve spindle 73 and places the mask over the patient, as shown in Fig. 1. The selector valve may be set in any position and will have no effect on the administration of the anesthetic gas mixture during normal respiration by the patient. Under these conditions the patients inhalation produces a slight suction in the facemask and chamber 29 of the non-rebreathing valve 16, causing the anesthetic mixture from the delivery conduit to be drawn inwardly. In response to such inhalation effort, the inhalation valve 30 opens and the exhalation valve 44 remains closed. As the patient exhales, a slight positive pressure is created which closes inhalation valve '30 and unseats exhalation valve 44 so that the gases of exhalation pass, without restriction, to the atmosphere through the valve openings 24.

When the anesthetist desires to assist the patients respi ration, or to force gas into the patients lungs independently of the patients own efforts, the selector valve '76 is positioned so that the diaphragm chamber 68 is placed in communication with the delivery inlet, as before described. This may be done by rotating spindle 78 to its extreme clockwise position in which diaphragm chamber 68 communicates with inlet conduit 26 through the tube 72, and the passage 70 to the atmosphere is closed. The anesthetist then periodically squeezes the breathing bag 12 producing a positive pressure, above atmospheric, in the delivery line. Such positive pressure is transmitted against the inhalation check valve 30 causing it to open as indicated in dotted lines in Fig. 2, thus producing a positive pressure in the valve chamber 29 and in the facemask connected thereto. Simultaneously, the positive delivery pressure is transmitted through tube 72 to diaphragm chamber 68, thereby producing an actuating force against diaphragm 6%). It will be seen that the positive pressure thus applied acts both against the underside of the exhalation check valve and against the top of diaphragm 60. However, as

previously described, the greater force is produced by the diaphragm which is sufiicient to seat and thereby close the exhalation valve. Thus, the diaphragm 6t) responds automatically to positive delivery pressure, preventing the dissipation' of such pressure through the exhalation valve, so that the delivery gas, under positive pressure, may be forced into the patients lungs.

When the anesthetist releases the pressure thus applied externally to the breathing bag, the delivery gas pressure returns to atmospheric. The muscular contraction of the patients chest wall then forces gas outwardly, as occurs during normal exhalation, into the valve chamber 29 and thence through exhalation valve 44 to the atmosphere. It will be seen that the gas pressure in chamber 68 acting downwardly on the diaphragm 60 is equal to the delivery pressure and thus returns to atmospheric pressure when the anesthetist releases the breathing bag. Consequently, there is no difierential pressure acting on the diaphragm 7 and the exhalation valve '46 is permitted to open freely following such forced inflation, in substantially the same manner as during normal respiration.

The non-rebreathing valve also may be utilized as described above for the assisted respiration of a patient with the valve 76 positioned in any of the intermediate positions, in which the diaphragm chamber is open both to the delivery conduit and to the atmosphere. The use of any of these positions provides an additional safeguard in the operation of the device. It will be seen, for example, that by maintaining a vented opening to the atmosphere a self-sustaining diaphragm pressure, such as might prevent normal exhalation by the patient, is prevented from occurring. When the valve 76 is positioned in its extreme clockwise position, the diaphragm chamber is completely cut off from the upstream side of the breathing circuit and is open only to the atmosphere. In this position of the selector valve, the diaphragm is inactivated so that the non-rebreathing valve may be used during normal respiration but will not act in response to positive delivery pressure to close the exhalation valve.

Although the non-rebreathing device 16, as shown in Fig. 2, is provided with a disk 61 by which the force of the diaphragm is transmitted to the exhalation checkvalve,

it should be understood that such an intermediate device is not essential and may be omitted. However, when omitted, the diaphragm 60 should be provided with'a sufficient amount of slack, or be of a conventional type of construction incorporating corrugations, or similar means, so that it may be extended far enough to bear against and act on the exhalation check valve substantially without the creation of any tension therein.

Alternative arrangements for automatically occluding the exhalation check valve during assisted pressure respiration, using the same administering circuit as shown in Fig. 1, are shown in Figs. 6 and 7. As shown in 'Fig. 6, an alternative construction comprises the use of a'closure plate 104 which is clamped by a seating ring 106 against the retainer cup 4-6 so as to seal the peripheral edges of a diaphragm 108. The plate 104 receives the tube 72 in the same manner as in the embodiment shown in Fig. 2. However, in place of the direct opening to the atmosphere, the plate 104 is equipped with pressure relief valve 11% having vent openings 111, in which a closure valve disk 112 is seated by a spring 114 against an exit passage 116 from the diaphragm chamber. The alternative of 'Fig. 6 does not include a selector valve by which the diaphragm 108 may be inactivated. Thus, whenever the anesthetist imposes a positive super-atmospheric pressure on the upstream side of the non-rebreathing valve, the diaphragm 108 will be actuated to close the exhalation check valve 46. However, the pressure relief valve 110 may be set at any predetermined pressure such as by adjustment of the cap 118 so that when a predetermined positive pressure exists in the diaphragm chamber, the chamber will be vented to the atmosphere and thus prevent a possible hazard to the patient.

The alternative construction of Fig. 7 illustrates the use of an alternative type of bellows diaphragm identified at 120 in place of the diaphragms 60 and 1&8 shown in Figs. 2 and 6. The bellows diaphragm 120 includes one or more corrugations 121 which permit extension of the diaphragm without the creation of tension in the side walls thereof. In this construction an intermediate disk for transmitting the force of the diaphragm is not used. The remainder of the valve is identical to the structure shown or described in Fig. 6. However, the diaphragm 120, also, may be incorporated in the valve structure shown in Fig. 2. I v

The invention is not limited to the specific embodiments herein illustrated and described, but may be used in other ways without departure from its spirit, as defined by the following claims.

I claim: 7

1. An anesthetic administering apparatus for administering an inhalent anesthetic gas mixture to a patient comprising a source of an anesthetic gas mixture, a delivery system, including valve means at the terminal end thereof effective to prevent reverse flow of gas in said delivery system, means connecting said delivery system with the patients respiratory tract, a collapsible breathing reservoir forming a part of said delivery system adapted to be compressed externally to create a positive pressure therein, a discharge system for conducting gases of exhalation from the patient to the atmosphere including discharge valve means which permits gas to flow only to the atmosphere when open, pressure responsive means operative to close said discharge valve means when energized,

and means communicating with said delivery system for applying the gas pressure therein to said pressure responsive means, whereby when said breathing bag is compressed to create a positive delivery pressure said pressure responsive means is energized and the flow of gas through said discharge valve means is prevented.

2. A non-rebreathing anesthetic administering circuit comprising a breathing chamber adapted to be placed in communication with a patients respiratory tract, a source of an anesthetic gas mixture, a delivery system for supplying the anesthetic gas mixture from said source to said breathing chamber, including a delivery check-valve at its terminal end preventing gas flow from said chamber into the delivery system, a collapsible chamber in said delivery system adapted to be externally compressed to create a positive delivery pressure therein, a discharge system leading from said chamber to the atmosphere including a discharge check-valve permitting gas flow only from the chamber to the atmosphere, and means, operatively associated with said discharge check-valve, responsive to the delivery pressure, to close said check-valve when said collapsible chamber is compressed to create a positive delivery pressure.

3. An anesthetic administering apparatus comprising means defining a breathing chamber adapted to be placed in communication with a patients respiratory tract, a source of anesthetic gas, a delivery system connecting said source with said breathing chamber for delivering an anesthetic mixture to said chamber, including an inlet check-valve at its terminal end permitting flow in only one direction through said delivery system, means forming a part of said delivery system operable to produce a positive delivery pressure therein, a discharge system forming an outlet from said chamber to the atmosphere through which gases from said chamber are discharged, including an outlet check-valve limiting the gas flow therethrough to one direction, a pressure responsive diaphragm responsive to the pressure in said delivery system, effective to close said discharge check-valve when activated by a positive differential between said delivery pressure and atmosphere pressure, said diaphragm being exposed on one side to the atmosphere and on the other side to a diaphragm chamber communicating with said delivery circuit, theeffective area of said diaphragm being larger than the effective seating area of the exhalation outlet check valve, and said diaphragm having vent means to the atmosphere to prevent a self-sustaining positive chamber pressure.

4. Apparatus for administering an anesthetic gas mixture, as set forth in claim 3, wherein said venting means comprises a pressure relief valve device effective to limit the maximum pressure attainable in said diaphragm chamber.

5. A valve device for anesthetic breathing circuits comprising, a valve body defining a breathing chamber and a passage communicating therewith adapted to be connected to an inhaler through which a patient breathes during administration of an anesthetic gas mixture, a conduitreceiving portion of said valve body having an inlet passage terminating in an inlet opening in said chamber, an inhalation check-valve disposed in said chamber to close against said inlet opening except when gas is delivered into said chamber therethrough, means defining a discharge outlet opening from said chamber and terminating externally of said housing, exhalation check-valve means disposed outside of said chamber effective to act inwardly against said outlet opening except when gas is discharged therethrough, means supported by said valve housing defining a second chamber, a pressure responsive diaphragm element forming a movable closure for said chamber, the outer side of which is exposed externally of said housing, said diaphragm element being adapted and arranged, when actuated, to act upon said exhalation check-valve so as to seal it against said discharge opening, conduit means forming a communication passage between said inlet passage and said second chamber, and an opening in said second chamber communicating with the atmosphere having pressure responsive means cooperatively associated therewith to be normally seated against said opening and to be unseated when the pressure in said second chamber raises to a predetermined maximum.

6. A valve device for anesthetic breathing circuits comprising, a valve body defining a breathing chamber and a passage communicating therewith adapted to be con nected to an inhaler through which a patient breathes during administration of an anesthetic gas mixture, a conduit-receiving portion of said valve body having an inlet passage terminating in an inlet opening in said chamber, an inhalation check-valve disposed in said chamber to close against said inlet opening except when gas is delivered into said chamber therethrough, means defining a discharge outlet opening fromsaid chamber and terminating externally of said housing, exhalation check-valve means disposed outside of said chamber effective to act inwardly against said outlet opening except when gas is discharged therethrough, means supported by said valve housing defining a second chamber, a pressure responsive diaphragm element forming a movable closure for said chamber, the outer side of which is exposed externally of said housing, said diaphragm element being adapted and arranged, when actuated, to act upon said exhaltion checkvalve so as to seal it against said discharge opening, conduit means forming a communicating passage between said inlet passage and said second chamber, an opening in said second chamber communicating with the atmosphere and an adjustable selector valve means etfective alternatively to close said opening or close said conduit means forming a communicating passage between said inlet passage and said second chamber.

7. A valve device according to claim 6 wherein said selector valve means is so constructed that when disposed in one extreme position it is effective to close said opening, and when disposed in its opposite extreme position is elfective to close said conduit means, and when disposed in positions intermediate said extreme positions is efiective to proportionately occlude the said opening and said conduit means.

8. A valve device for anesthetic breathing apparatus comprising a hollow cylindrical valve body defining a breathing chamber, one end thereof being open and adapted to be connected to an inhaler, a discharge opening at the opposite end of said valve body forming an exhalation outlet from said breathing chamber, a discharge breathing check-valve operatively associated with said exhalation outlet to permit only discharge flow therethrough, a housing supported by said cylindrical body forming a diaphragm chamber and having a pressure responsive diaphragm forming one wall thereof disposed in confronting relation to said discharge check-valve, said diaphragm having a larger effective area than said exhalation check-valve and being efiective in response to positive pressure in said diaphragm chamber to prevent opening of said discharge check-valve, means forming an inlet to said breathing chamber adapted to receive a conduit for delivering inhalation anesthetic gases thereto and through which positive pressure may be applied to said breathing chamber for assisting inhalation, said inlet having a unidirectional check-valve at the inner terminal end thereof to permit gas to flow only from said inlet into said chamber, a passage connecting said inlet with said diaphragm chamber and means forming a vent discharge from said diaphragm chamber through which positive pressure is adapted to be relieved to prevent a self-sustaining positive chamber pressure.

References Cited in the file of this patent UNITED STATES PATENTS 2,453,475 Tobias Nov. 9, 1948 

